JPS63133502A - Nonlinear resistor and manufacture of the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a non-linear resistor mainly composed of zinc oxide used in lightning arresters, etc., and a method for manufacturing the same. The present invention relates to a nonlinear resistor in which the form of a cobalt raw material added as a subcomponent is improved, and a method for manufacturing the same.

(Prior Art) Lightning arresters are used to protect the power system by suppressing abnormal voltages generated in the power system.

Lightning arresters use nonlinear resistors that exhibit insulating properties at normal voltages and have a low resistance value when abnormal voltages are applied. A nonlinear resistor is generally called a varistor, and a typical example thereof is one whose main component is zinc oxide.

In general, non-linear resistors made of metal oxides used in lightning arresters etc. mainly contain zinc oxide (ZnO) and Bi.
, Sb, Co, Mn, Or, Ni.

It contains components such as 3i and Al1, and is manufactured by mixing raw materials, granulation molding, sintering, and attaching electrodes to both ends.

To explain in more detail, zinc oxide and the oxide or the a1 component raw material that will replace the oxide through sintering are thoroughly mixed with water and an organic binder, and then granulated with a spray dryer etc., and the resulting granulated powder is made of coarse particles. A manufacturing method is known that removes secondary agglomerated particles, places them in a mold, forms them, and sinters them to eliminate voids and pinholes that occur inside the resistor, thereby preventing a decrease in surge resistance and energized life. ing. (Unexamined Japanese Patent Publication No. 1983-(Problems to be Solved by the Invention)) In recent years, electric power systems have become larger in capacity and higher in voltage in order to reduce transmission costs, and as a result, lightning arresters for 500 KV have been put into practical use. Near conventional 1000 KV (UHV)
Lightning arresters are also planned. The non-linear resistors used in these lightning arresters must handle extremely large surge energy, and due to characteristic problems such as the tendency to cause imbalance in the non-linear resistors, the number of non-linear resistors is limited to a few, and the number of non-linear resistors is inevitably reduced. The capacity of the body can be increased. However, since the thickness is limited by the limiting voltage of the lightning arrester, etc., the diameter must be increased.

In this way, the shape of one nonlinear resistor for 500 KV and 100 OKV has a diameter of 100 to 120 m and a thickness of 20 to 45 m due to deformation during sintering and economic efficiency. Such non-linear resistors are difficult to sinter and often lead to variations in heat dissipation and resistance properties, resulting in deterioration, and a stable manufacturing method has been desired.

The present invention has been made in view of the above points, and an object of the present invention is to provide a non-linear resistor and a method for manufacturing the same, which improves stability during sintering and improves discharge withstand characteristics, which are closely related to the above-mentioned drawbacks. shall be.

(Structure of the Invention) (Means for Solving the Problems) In order to achieve the above object, in the production method of the present invention, the cobalt raw material is cobalt tetraoxide (CO304), and boron nitride (BN) is used in advance. ) is characterized in that it uses wet-mixed raw materials.

(Function) The cobalt raw material is cobalt tetra/trioxide (CO304), and according to the present invention, which uses a raw material that has been wet-mixed with BN in advance, the cobalt raw material has few secondary agglomerated particles and has good dispersibility. During mixing, cobalt tetraoxide and trioxide are dispersed uniformly into zinc oxide (ZnO), and CO3O is roughly dispersed.
Since 4 decomposes into CoO and O during the sintering process, oxygen can be supplied sufficiently and uniformly into the sintered body. Therefore, the inside of the element becomes an oxidizing atmosphere, creating conditions desirable for the nonlinear resistor, and normal reactions proceed.

As a result, it is possible to provide a method for manufacturing an element with less variation within the element and improved discharge resistance characteristics.

(Example) Hereinafter, a non-linear resistor and a method for manufacturing the same according to an example of the present invention will be described.

Bismuth oxide (BtzO3), cobalt tetraoxide (C
0304), manganese dioxide (81102>), chromium oxide (Cr02), and silicon dioxide (Si02), respectively.
511101%, antimony oxide (SbzOs), nickel oxide (NIP) each at 1 mo1%, aluminum oxide (AgzOs) at 0.0025 wt%,
Accurately weigh the remainder as zinc oxide.

Next, for example, 1 of the amount of CO3O4 is added to cobalt tetra/trioxide.
Add 00 ppm boron nitride (lung) and wet mix. After that, it is dispersed together with other raw materials and organic binders such as water, dispersant, binder, and lubricant, and then put into a mixing device and dispersed.
Mix.

The mixture is then spray granulated using a spray dryer. These granulated powders were placed in a mold, molded, and fired in air at 500°C to remove the added organic binders.
Preliminary firing is performed at ℃ to form a high resistance layer on the side surface.

Thereafter, a high-resistance material is applied, sintered in air at 1200'C, both surfaces polished, color coated, and color fired. A non-linear resistor having a diameter of 100 m and a thickness of "2251I11" was obtained by attaching aluminum metallic electrodes on both flat surfaces.

The discharge resistance of the nonlinear resistor completed as described above was measured. Figure 1 shows the results. The discharge withstand characteristics are 2.
Using a 5 mS rectangular wave current, the energy withstood after being applied five times was shown in a distribution diagram.

a is CO3 mixed with 1100 pp BN according to the invention
For comparison, B shows a model using an untreated cobalt tetraoxide raw material, and C shows a model using a conventional cobalt raw material (Cod).

FIG. 2 shows the relationship between the amount of boron nitride used for mixing with the cobalt raw material and the pass rate in the discharge capacity characteristic of 200 J/cc. This result shows that improving the dispersibility of the cobalt raw material by mixing it with boron nitride has a large impact on the discharge withstand characteristics. That is, it is shown that by using a CO304 raw material wet-mixed with boron nitride in which the amount of boron nitride is 1100 pp or more relative to the amount of CO3O4, the discharge withstand characteristics can be improved.

From these results, co3o mixed wet with BN
It is clear that a nonlinear resistor having excellent discharge withstand characteristics can be obtained by using the four raw materials.

As mentioned above, cobalt tetraoxide (C) is used as a cobalt raw material.
O304), and boron nitride (BN)
It is not clear why the discharge withstand characteristics were improved by wet mixing with CO3O4.
is co3o4→3co during the sintering process.

It is known that it changes to +0. It is thought that the oxygen released at this time has a favorable effect on the reaction for producing the nonlinear resistor. Regardless of the non-linear resistor, it is known that sintering oxide ceramics in air or in an oxidizing atmosphere with atmospheric oxygen is a condition for obtaining good characteristics.

Therefore, during sintering, if sufficient oxygen does not reach inside the element body, the normal production reaction is inhibited and the properties are rarely affected. It is desirable that oxygen be supplied from the nonlinear resistor itself, as shown in the figure.

Even if oxygen is not sufficiently distributed to the inside of the sintered body only by supplying oxygen from outside the sintered body, an oxygen atmosphere is formed by supplying oxygen from the inside, and the normal production reaction progresses to the inside, causing structural defects. It is thought that a homogeneous non-linear resistor with no cracks was obtained, and the discharge withstand characteristics were improved.

Furthermore, by wet-mixing the cobalt raw material with boron nitride (BN) in advance, good discharge withstand characteristics were exhibited.

The cobalt raw material itself has strong agglomeration and many secondary agglomerated particles. However, by wet mixing with boron nitride, the secondary agglomerated particles are broken and a good dispersion state can be obtained. The situation is shown in Figure 3. In the figure, temple is not wet mixed with boron nitride, and e is ioo for cobalt raw material.
f shows the particle size distribution of the cobalt raw material wet-mixed with 500 ppm of boron nitride, and f shows the particle size distribution of the cobalt raw material wet-mixed with 500 ppm of boron nitride. It is clear that wet mixing with boron nitride improves the dispersion state of the cobalt raw material. As a result, it is thought that the cobalt raw material and zinc oxide (ZnO) are well dispersed, uniform grain growth occurs, and excellent discharge withstand characteristics can be obtained.

In addition, in this experimental example, the shape of the non-linear resistor is 100X''22
Although I showed the one with rrm, I confirmed that the same effect can be obtained even with a small word. The effect of increasing the capacity of the nonlinear resistor is obvious for the reasons described above.

〔Effect of the invention〕

As explained in detail above, according to the present invention, cobalt tetraoxide (CO304) is used as a cobalt raw material, and by wet-mixing it with boron nitride (BN) in advance, the cobalt raw material and oxidized Zinc can be homogeneously dispersed, and oxygen can be supplied from inside the element body during the sintering process, so that the formation reaction can proceed uniformly and normally within the element body, and there are no structural defects even inside the element body. A homogeneous sintered body can be obtained. As a result, it is possible to provide a nonlinear resistor with extremely high discharge withstand characteristics using an economical manufacturing method.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a comparison of discharge withstand characteristics between an embodiment of the non-linear resistor manufacturing method of the present invention and a conventional example, and Figure 2 is a diagram showing the amount of boron nitride mixed with the cobalt raw material and the passing of the discharge withstand test. FIG. 3 is a diagram showing a comparison of the particle size distribution of the cobalt raw material according to the size of boron nitride mixed with the cobalt raw material.

Claims (2)

[Claims] (1) A nonlinear resistor containing zinc oxide as a main component and cobalt as a subcomponent, wherein the cobalt is cobalt tetraoxide and trioxide wet mixed with boron nitride. (2) A method for manufacturing a non-linear resistor in which zinc oxide is the main component and cobalt is added as a sub-component, wherein the cobalt is wet-mixed with boron nitride in advance using cobalt tetra-trioxide. Method of manufacturing a resistor.